Oh. The 2013 version didn't come with a changelog.
Here's a diff on the source:
Code:
Only in 2012/com/ni/rio: NiRioSrv.java
Only in 2012/com/ni/rio: VxWorks.java
Only in 2012/com/ni/rio: package.html
Only in 2012/edu/wpi/first: testing
Files 2012/edu/wpi/first/wpilibj/ADXL345_I2C.java and 2013/edu/wpi/first/wpilibj/ADXL345_I2C.java differ
Files 2012/edu/wpi/first/wpilibj/Accelerometer.java and 2013/edu/wpi/first/wpilibj/Accelerometer.java differ
Files 2012/edu/wpi/first/wpilibj/AnalogChannel.java and 2013/edu/wpi/first/wpilibj/AnalogChannel.java differ
Files 2012/edu/wpi/first/wpilibj/AnalogTrigger.java and 2013/edu/wpi/first/wpilibj/AnalogTrigger.java differ
Files 2012/edu/wpi/first/wpilibj/AnalogTriggerOutput.java and 2013/edu/wpi/first/wpilibj/AnalogTriggerOutput.java differ
Files 2012/edu/wpi/first/wpilibj/CANJaguar.java and 2013/edu/wpi/first/wpilibj/CANJaguar.java differ
Files 2012/edu/wpi/first/wpilibj/Compressor.java and 2013/edu/wpi/first/wpilibj/Compressor.java differ
Only in 2013/edu/wpi/first/wpilibj: Controller.java
Files 2012/edu/wpi/first/wpilibj/Counter.java and 2013/edu/wpi/first/wpilibj/Counter.java differ
Files 2012/edu/wpi/first/wpilibj/Dashboard.java and 2013/edu/wpi/first/wpilibj/Dashboard.java differ
Files 2012/edu/wpi/first/wpilibj/DigitalInput.java and 2013/edu/wpi/first/wpilibj/DigitalInput.java differ
Files 2012/edu/wpi/first/wpilibj/DigitalModule.java and 2013/edu/wpi/first/wpilibj/DigitalModule.java differ
Files 2012/edu/wpi/first/wpilibj/DigitalOutput.java and 2013/edu/wpi/first/wpilibj/DigitalOutput.java differ
Files 2012/edu/wpi/first/wpilibj/DoubleSolenoid.java and 2013/edu/wpi/first/wpilibj/DoubleSolenoid.java differ
Files 2012/edu/wpi/first/wpilibj/DriverStation.java and 2013/edu/wpi/first/wpilibj/DriverStation.java differ
Files 2012/edu/wpi/first/wpilibj/DriverStationLCD.java and 2013/edu/wpi/first/wpilibj/DriverStationLCD.java differ
Files 2012/edu/wpi/first/wpilibj/Encoder.java and 2013/edu/wpi/first/wpilibj/Encoder.java differ
Files 2012/edu/wpi/first/wpilibj/GearTooth.java and 2013/edu/wpi/first/wpilibj/GearTooth.java differ
Files 2012/edu/wpi/first/wpilibj/Gyro.java and 2013/edu/wpi/first/wpilibj/Gyro.java differ
Files 2012/edu/wpi/first/wpilibj/HiTechnicCompass.java and 2013/edu/wpi/first/wpilibj/HiTechnicCompass.java differ
Files 2012/edu/wpi/first/wpilibj/I2C.java and 2013/edu/wpi/first/wpilibj/I2C.java differ
Files 2012/edu/wpi/first/wpilibj/IterativeRobot.java and 2013/edu/wpi/first/wpilibj/IterativeRobot.java differ
Files 2012/edu/wpi/first/wpilibj/Jaguar.java and 2013/edu/wpi/first/wpilibj/Jaguar.java differ
Files 2012/edu/wpi/first/wpilibj/Joystick.java and 2013/edu/wpi/first/wpilibj/Joystick.java differ
Files 2012/edu/wpi/first/wpilibj/Kinect.java and 2013/edu/wpi/first/wpilibj/Kinect.java differ
Files 2012/edu/wpi/first/wpilibj/KinectStick.java and 2013/edu/wpi/first/wpilibj/KinectStick.java differ
Files 2012/edu/wpi/first/wpilibj/Module.java and 2013/edu/wpi/first/wpilibj/Module.java differ
Only in 2013/edu/wpi/first/wpilibj: NamedSendable.java
Files 2012/edu/wpi/first/wpilibj/PIDController.java and 2013/edu/wpi/first/wpilibj/PIDController.java differ
Files 2012/edu/wpi/first/wpilibj/PWM.java and 2013/edu/wpi/first/wpilibj/PWM.java differ
Files 2012/edu/wpi/first/wpilibj/Preferences.java and 2013/edu/wpi/first/wpilibj/Preferences.java differ
Files 2012/edu/wpi/first/wpilibj/Relay.java and 2013/edu/wpi/first/wpilibj/Relay.java differ
Files 2012/edu/wpi/first/wpilibj/RobotBase.java and 2013/edu/wpi/first/wpilibj/RobotBase.java differ
Files 2012/edu/wpi/first/wpilibj/RobotDrive.java and 2013/edu/wpi/first/wpilibj/RobotDrive.java differ
Only in 2013/edu/wpi/first/wpilibj: Sendable.java
Files 2012/edu/wpi/first/wpilibj/SensorBase.java and 2013/edu/wpi/first/wpilibj/SensorBase.java differ
Files 2012/edu/wpi/first/wpilibj/SerialPort.java and 2013/edu/wpi/first/wpilibj/SerialPort.java differ
Files 2012/edu/wpi/first/wpilibj/Servo.java and 2013/edu/wpi/first/wpilibj/Servo.java differ
Files 2012/edu/wpi/first/wpilibj/SimpleRobot.java and 2013/edu/wpi/first/wpilibj/SimpleRobot.java differ
Files 2012/edu/wpi/first/wpilibj/Skeleton.java and 2013/edu/wpi/first/wpilibj/Skeleton.java differ
Only in 2012/edu/wpi/first/wpilibj: SmartDashboard.java
Only in 2012/edu/wpi/first/wpilibj: SmartDashboardPacketFactory.java
Files 2012/edu/wpi/first/wpilibj/Solenoid.java and 2013/edu/wpi/first/wpilibj/Solenoid.java differ
Only in 2013/edu/wpi/first/wpilibj: Talon.java
Files 2012/edu/wpi/first/wpilibj/Ultrasonic.java and 2013/edu/wpi/first/wpilibj/Ultrasonic.java differ
Files 2012/edu/wpi/first/wpilibj/Victor.java and 2013/edu/wpi/first/wpilibj/Victor.java differ
Files 2012/edu/wpi/first/wpilibj/buttons/AnalogIOButton.java and 2013/edu/wpi/first/wpilibj/buttons/AnalogIOButton.java differ
Files 2012/edu/wpi/first/wpilibj/buttons/Button.java and 2013/edu/wpi/first/wpilibj/buttons/Button.java differ
Files 2012/edu/wpi/first/wpilibj/buttons/JoystickButton.java and 2013/edu/wpi/first/wpilibj/buttons/JoystickButton.java differ
Only in 2013/edu/wpi/first/wpilibj/buttons: Trigger.java
Files 2012/edu/wpi/first/wpilibj/camera/AxisCamera.java and 2013/edu/wpi/first/wpilibj/camera/AxisCamera.java differ
Files 2012/edu/wpi/first/wpilibj/can/JaguarCANProtocol.java and 2013/edu/wpi/first/wpilibj/can/JaguarCANProtocol.java differ
Files 2012/edu/wpi/first/wpilibj/command/Command.java and 2013/edu/wpi/first/wpilibj/command/Command.java differ
Files 2012/edu/wpi/first/wpilibj/command/PIDCommand.java and 2013/edu/wpi/first/wpilibj/command/PIDCommand.java differ
Files 2012/edu/wpi/first/wpilibj/command/PIDSubsystem.java and 2013/edu/wpi/first/wpilibj/command/PIDSubsystem.java differ
Files 2012/edu/wpi/first/wpilibj/command/Scheduler.java and 2013/edu/wpi/first/wpilibj/command/Scheduler.java differ
Files 2012/edu/wpi/first/wpilibj/command/Subsystem.java and 2013/edu/wpi/first/wpilibj/command/Subsystem.java differ
Files 2012/edu/wpi/first/wpilibj/communication/FRCCommonControlData.java and 2013/edu/wpi/first/wpilibj/communication/FRCCommonControlData.java differ
Files 2012/edu/wpi/first/wpilibj/communication/FRCControl.java and 2013/edu/wpi/first/wpilibj/communication/FRCControl.java differ
Files 2012/edu/wpi/first/wpilibj/communication/UsageReporting.java and 2013/edu/wpi/first/wpilibj/communication/UsageReporting.java differ
Only in 2012/edu/wpi/first/wpilibj/fpga: DMAChannelDescriptors.java
Only in 2012/edu/wpi/first/wpilibj/fpga: package.html
Files 2012/edu/wpi/first/wpilibj/image/BinaryImage.java and 2013/edu/wpi/first/wpilibj/image/BinaryImage.java differ
Only in 2013/edu/wpi/first/wpilibj/image: CriteriaCollection.java
Files 2012/edu/wpi/first/wpilibj/image/NIVision.java and 2013/edu/wpi/first/wpilibj/image/NIVision.java differ
Only in 2013/edu/wpi/first/wpilibj: livewindow
Only in 2012/edu/wpi/first/wpilibj: networktables
Files 2012/edu/wpi/first/wpilibj/smartdashboard/SendableChooser.java and 2013/edu/wpi/first/wpilibj/smartdashboard/SendableChooser.java differ
Only in 2012/edu/wpi/first/wpilibj/smartdashboard: SendableGyro.java
Only in 2012/edu/wpi/first/wpilibj/smartdashboard: SendablePIDController.java
Files 2012/edu/wpi/first/wpilibj/smartdashboard/SmartDashboard.java and 2013/edu/wpi/first/wpilibj/smartdashboard/SmartDashboard.java differ
Only in 2012/edu/wpi/first/wpilibj/smartdashboard: SmartDashboardData.java
Only in 2012/edu/wpi/first/wpilibj/smartdashboard: SmartDashboardNamedData.java
For more in-depth changes, see attached side-by-side diff log. Mostly LiveWindow stuff, network sending for them, and the new Talon speed controller.